Attending to speech and discrimination among its features are essential precursors to infants learning to extract meaning from it. One objective of this application is to isolate the features of speech and other acoustic signals that reinforce neonates and determine whether the features that are reinforcing change during the first six months of life. To reach this objective, auditory stimuli will be made contingent upon infants' suck duration and upon their rate of high-amplitude sucking. A second objective is to identify the features of auditory signals that are discriminated at birth and to determine whether the features that are discriminated change between birth and six months. To reach this objective, auditory stimuli will be used in a dishabituation procedure and as discriminative cues in chaining and multiple-schedule operant conditioning paradigms. Thus, for each goal we will employ converging operations across early infancy to assess the effects of segmental and suprasegmental, simple and multidimensional acoustic manipulations. The data will clarify the development of attention to speech and its discrimination. A third objective is to determine the characteristics and chart the development of vocalization across the first year of life. To reach this objective, audio recordings are made longitudinally of normal and hearing-impaired infants, and of normal infants whose parents are hearing impaired. These recordings are subjected to systematic observational and acoustic scoring. BIBLIOGRAPHIC REFERENCES: Butterfield, E. C., and Cairns, G. F., Jr. Process defects that might underlie aberrant language development. In N. R. Ellis (Ed.), Aberrant Development in Infancy. New York: Erlbaum Associates 1975. Butterfield, E. C., and Cairns, G. F., Jr. The infant's auditory environment. In Tjossem, T. D. (Ed.), Intervention Strategies for High Risk Infants and Young Children. Baltimore, Maryland: University Park Press, in press.